e correlation in angular momentum exchange. We may possibly explain this through observing the general fact that there are no secular terms in planetary semimajor axes up to second-order perturbation theories (cf. Brouwer & Clemence 1961; Boccaletti & Pucacco 1998). This means that the planetary orbital energy (which is directly related to the semimajor axis a) might be much less affected by perturbing planets than is the angular mometum exchange (which relates to e). Hence， the eccentricities of Venus and Earth can be disturbed easily by Jupiter and Saturn， which results in a positive correlation in the angular momentum exchange. On the other hand， the semimajor axes of Venus and Earth are less likely to be disturbed by the jovian planets. Thus the energy exchange may be limited only within the Venus–Earth pair， which results in a negative correlation in the exchange of orbital energy in the pair.
As for the outer jovian planetary subsystem， Jupiter–Saturn and Uranus–Neptune seem to make dynamical pairs. However， the strength of their coupling is not as strong compared with that of the Venus–Earth pair.
5 ± 5 × 1010-yr integrations of outer planetary orbits
Since the jovian planetary masses are much larger than the terrestrial planetary masses， we treat the jovian planetary system as an independent planetary system in terms of the study of its dynamical stability. Hence， we added a couple of trial integrations that span ± 5 × 1010 yr， including only the outer five planets (the four jovian planets plus Pluto). The results exhibit the rigorous stability of the outer planetary system over this long time-span. Orbital configurations (Fig. 12)， and variation of eccentricities and inclinations (Fig. 13) show this very long-term stability of the outer five planets in both the time and the frequency domains. Although we do not show maps here， the typical frequency of the orbital oscillation of Pluto and the other outer planets is almost